1. Field of the Invention
The present invention relates to a method and a device for operating an internal combustion engine, in which the fuel is supplied to at least one combustion chamber via at least one injector, and in which a characteristic curve of the injector is adjusted.
2. Description of Related Art
Internal combustions engines having gasoline injection into an intake manifold as well as direct gasoline injection into the particular combustion chambers are known. The gasoline is injected by at least one injector. This injector must cover a wide quantity range. As a rule, the range extends from the idle point, or also from a fired overrun, which defines a minimum quantity, to full load at high speeds, which defines a maximum quantity.
The fuel quantity injected by the injector ideally has a linear correlation to the opening time of the injector. However, a very broad linear range means that the cost of manufacturing the injector is comparatively high. This manufacturing cost increases in proportion to the need to minimize undesired deviations from the linearity, particularly in the low-volume range. In this range, in particular, the scatter between the individual injectors may be comparatively high, which makes generally applicable and non-valve-specific corrections more difficult.
To prevent, or at least limit, the injection of different fuel quantities into the individual combustion chambers of an internal combustion engine, a method known from the market is used to set a lower limit to the minimum injection time. An adjustment by which the characteristic curve of an injector is adjusted to the actual conditions is also possible. In an internal combustion engine having direct gasoline injection, for example, the running smoothness while idling in stratified-charge mode may be used for an adjustment of this type. In internal combustion engines having intake manifold injection, a so-called “single-cylinder lambda regulation” method may be used. While the first method is usable only for specific internal combustion engines, the second method requires a comparatively well-defined operating point.
An object of the present invention is to provide a method which enables the injection performance of an injector to be tested even when the internal combustion engine is operating in normal mode.